Explosive blasting in construction and mining operations requires drilling a large number of blast holes into the ground, typically in a grid pattern across the entire blast site, placing explosive charges into the holes and then detonating the charges. The explosion fragments solid rock by sending shock waves through the ground, which makes the process of removing the rock significantly easier.
Before the explosives are detonated, the blast holes are covered with non-volatile matter, such as crushed gravel and water, in a process commonly referred to as stemming. Each of the blast holes is stemmed to prevent high velocity explosive blast gases from escaping through the top of the blast holes. Minimizing or preventing the escape of the blast gases is important for at least two reasons. First, creating the shock wave that fragments rock requires a buildup of pressurized gas. If the blast gases were permitted to escape out of the blast hole, the effectiveness of the blast would be greatly diminished. Second, stemming the blast holes makes the detonation much safer by minimizing the amount of material that is projected from the blast hole.
Often times the stemming process is carried out using front end loaders, track hoes, skid loaders, etc. Other times, due to the blast site conditions, hand carrying buckets of stemming material to each blast hole and pouring the material into the hole is required. An advantage of this method is that the worker can inspect the material as it fills the hole. This is important because material that is too large or foreign materials may cause the blast to become less effective or even dangerous. Given the large number of blast holes that are present at each blast site, the stemming process has historically been very labor intensive and time consuming.
Another method for stemming holes has been to fill a large dump truck. This process involves, for example, filling the truck with stemming material using a front loader, driving the truck to the blast site, pouring the stemming material into a blast hole using a conveyor system mounted to the truck, and then driving to the next blast hole and repeating the filling process. However, using this method does not provide an opportunity for the truck operator to inspect the stemming material as it fills the hole. Also, due to their large size, these types of large trucks are not well suited for sites have restricted or limited space.
Accordingly, there is a need for an apparatus that enables stemming material to be quickly and conveniently poured into a blasting hole in locations having restricted or limited space and that allows a worker to directly inspect the material as it is poured.